| Name | Street | Number | Occupation |
|---|---|---|---|
| Obarrio, Manuel | Piedras | 84 | lawyer |
| Obejero, Eduardo | Florida | 402 | medical doctor |
| Obligado & Co. | Balcarce | 61 | agents |
| Obligado, Antonio V. y Hnos. | Perú | 157 | lawyers |
| Obligado, Justino | Florida | 22 | lawyer |
| Obligado, L. | Tacuarí | 9 | estanciero |
| Obligado, Luis | Tacuarí | 9 | lawyer |
| Ocampo, Benigno | Reconquista | 43 | lawyer |
| Ocampo Hnos. | Florida | 194 | brokers |
| Ocampo, Sackmann & Co. | Cuyo | 755 | saw-mills |
| Ocampo & Dimet, | San Martín | 170 | brokers |
| Ocampo, Daniel | Perú | 147 | lawyer |
| Ocampo, Eusebio | Artes | 38 | lawyer |
| Ocampo, Manuel | Perú | 5 | estanciero |
| Ocantos, Jos&eacue; A. | Defensa | 73 | lawyer |
| Ocantos, Mar. J. | Santa Lucía | 84 | medical doctor |
| Ochoa, E. P. | Uruguay | 228 | saw-mill |
| O'Connor & Co. | Cerrito | 354 | timber-yard |
| O'Donnell & Co. | Artes | 478 | consignees |
| O'Donnell, Elias sen. | Tucumán | 821 | accountant |
| O'Donnell, Elias | Tucumán | 821 | lawyer |
| O'Farrell, Santiago Gregorio | Alsina | 159 | lawyer |
| O'Gorman, Charles | Garantías | 309 | auctioneer |
| O'Gorman, Edward | Lavalle | 431 | |
| O'Jea, Anthony | Victoria | 395 | consignee |
| Ojeda, Olegario | Paraguay | 388 | lawyer |
| Olaso Aldazábal, J. C. de & Co. | Rivadavia | 200 | dry goods |
| Olaso & Ayarragaray, | Victoria | 360 | grocers |
| Oliva & Schnabl, | Florida | 99 | oculists |
| Oliver & Picasso, | Chacabuco | 69 | lime-burners |
| Oliver, Ramón | San Martín | 151 | lawyer |
| Olivero, José | Corrientea | 674 | medical doctor |
| Oltmann, Eduard | Cangallo | 343 | dentist |
| Oltramare, Dr. G. | Cuyo | 314 | dentist |
| Oneto, J. & Son, | Piedad | 802 | miller |
| Operaio Italiano, | Cuyo | 267 | paper |
| Orey, Erasto Rodríguez | Victoria | 317 | director, Banco Nacional |
| Oostendorp, A. | San Martín | 151 | exporter, estanciero |
| Oreyro, Ventura | Piedad | 74 | ship-broker |
| Oro, Belisario | Bolívar | 103 | lawyer |
| Ortega, Francisco | Lavalle | 436 | medical doctor |
| Ortelli, José | Balcarce | 40 | lighterman |
| Ortelli, José | Corrientes | 253 | paint-shop |
| Ortiz, Adolfo S. | Perú | 282 | consignee |
| Ortiz, Julián | Venezuela | 398 | consignee |
| Ortiz Basualdo, Luis | Florida | 36 | lawyer |
| Ortiz Basualdo, M. | Florida | 74 | lawyer |
| Ortiz de Zárate, R. | Ombú | 121 | broker |
| Osborn, General Thomas | Lavalle | 136 | U.S. Minister |
| Osborne & Co. | Chacabuco | 65 | sewing machines |
| Ostermann, Albert | Buen Orden | 165 | furniture |
| Oteiza, Alberto | Bolívar | 81 | lawyer |
| Otero, I. R. | Defensa | 479 | estanciero |
| Otero, Ramos | Cangallo | 1121 | director, FCO |
| Otonello, J. | Rincon | 156 | carpenter |
| Otto, H. | Maipú | 137 | furniture |
| Oyuela, Ignacio | Venezuela | 266 | civil engineer |
M. G. & E. T. Mulhall, Handbook of the River Plate (London: Trübner & Co., 1885) pages 673-674.
Guía Mensual de Kidd, Imprenta de J. H. Kidd, setiembre de 1884, pages 76-78, 151, 155-156.